The directional characteristics of ocean surface and other water waves have been measured by submerged arrays of pressure-sensing transducers in which there is a general estimate of water surface slope obtained by subtracting the pressures sensed under the waves at two or more points and dividing by the distance between the sensors. However, the difference in pressure between any two sensors of a typical array is generally very small compared to the large absolute pressures that the transducers are required to record. The water surface slope has accordingly been calculated by subtracting two very large numbers in order to generate a very small number. This has contributed inaccuracies to measurements of wave characteristics.